Semiconductor devices are typically designed using increasingly smaller sizes or geometries, thereby promoting the importance of wire layers made of Al, Cu, etc. The use of wire layers made of Al, Cu, etc. enhances the importance of barrier metal layers that, for example, prevent diffusion of silicon from a semiconductor substrate, a silicon-containing layer, etc. into a wire layer.
FIGS. 1 and 2 illustrate an example of a known barrier metal layer configuration. The example barrier metal layer configuration shown in FIGS. 1 and 2 is generally fabricated by forming an interlayer insulating layer 2 on a semiconductor substrate 1 having a series of previously formed basic components and then opening a contact hole in a portion of the interlayer insulating layer 2; forming first and second metal base layers 3a and 4a on a front face of the semiconductor substrate 1 containing the contact hole; forming a contact metal base layer 6a on a front face of the first and second metal base layers 3a and 4a to fill the contact hole; and forming a final barrier metal layer 5 and a contact metal layer 6 within the contact hole of the interlayer insulating layer 2 as shown in FIG. 2 via polishing such as chemical mechanical polishing (CMP).
In the known example of FIGS. 1 and 2, the first and second barrier metal layers 3a and 4a are made of various materials such as TiN/Ti, TaN/Ta and WN/W. The barrier metal layers 3a and 4a of the example shown in FIGS. 1 and 2 have a double-layer structure as in TiN/Ti, TaN/Ta and WN/W. Such a double-layer structure is typically used for the barrier metal layers 3a and 4a because using a single-layer structure formed using known barrier metal layers would provide undesirable polishing, barrier and contact characteristics.
Although the polishing, barrier and contact characteristics of the barrier metal layers 3a and 4a can be improved to a certain degree if the barrier metal layers 3a and 4a are formed using a double-layer structure, the overall thicknesses of the combined barrier metal layers 3a and 4a is increased. Of course, if the resistance of the wire layer is increased as a result of the increased thickness of the barrier metal layers 3a and 4a, the quality of a resultant semiconductor device is also significantly decreased. Furthermore, the barrier metal layers 3a and 4a formed using the known double layer structure also increases the number of overall process steps, thereby decreasing the overall productivity of a semiconductor fabrication process.